1. Technical Field
This disclosure relates to fastener apertures in general, and fastener apertures having an elongated geometry in particular.
2. Background Information
Traditional bolt holes have circular cross-sectional geometries. Circular bolt holes, however, are typically subject to relatively high stress concentrations. In order to reduce these high stresses, bolt holes can be configured having slotted geometries; e.g., elongated circular cross-sectional geometries, diamond shaped cross-sectional geometries, etc.
Slotted bolt holes are often formed using a milling process. For example, during the formation of an elongated circular bolt hole, a CNC milling machine begins removing material at a given point along the perimeter of the elongated circular geometry, and then finishes at the same point. Because of tolerances and machine runout, the milling machine almost never arrives at the exact coordinates of the starting point; i.e., the starting point and the ending point are almost always offset from one another. This offset ridge in the wall of the bolt hole creates a stress concentration that increases stress at that point. Additionally, depending on the tolerances of the CNC machine, this offset can be difficult to detect without using optical magnification equipment.